The dinosaur, Concavenator corcovatus, also known as "the hunchbacked hunter from Cuenca," lived 130 million years ago in what is now Cuenca, Spain.

Close to 6 metres long, the dinosaur was related to Carcharodontosaurus, an enormous predatory dinosaur that was possibly even longer than Tyrannosaurus rex.

The new dino's 'bizarre' hunchback look is a first for dinosaurs.

"One of the unique characteristics of Concavenator, unknown in any other dinosaur yet discovered, is the particular elongation of the last two vertebrae in front of the hip area that project their neural spines on the back of the animal, forming a kind of hump whose function is so far unknown," says lead author Dr Francisco Ortega.

Ancestral feathers

Like many modern birds, the dinosaur possessed "quill knobs," or small bumps on the forearms that generally hold feathers.

"This feature was also recognised in some small dinosaurs, very closely related to birds, such as Velociraptor," he says.

"Surprisingly, Concavenator, four times larger than Velociraptor, and a priori too primitive to have feathers, also has these little bumps."

This likely means the large Spanish dinosaur either had feathers, or some type of skin structure that was "an ancestral stage of the feathers in birds," according to Ortega.

He and colleagues Fernando Escaso and Jose Sanz made the determinations after studying the dinosaur's fossils, which represent the most complete carcharodontosaur and the first to show any evidence related to feathers.

Scientists have been mulling over the original function of feathers for quite some time. A few theories were that feathers, or feather-like structures, helped with thermal control or aerodynamics, giving the animal lift and thrust.

In this case, since the feathers appear to have just been on the dinosaur's forearms, the evidence "points to a display function," says Ortega, who adds that they could have also served some as of yet unknown purpose too.

With its pointy hump and possible feathers, the new dinosaur must have cut quite a figure in the wetlands of Early Cretaceous East-Central Spain, where it lived. It shared the area with other dinosaurs, birds, turtles, lizards, crocodiles, crustaceans and many other animals.

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At first, palaeontologists thought that carcharodontosaurs were limited to the southern continents, since most such fossils were found in places like South America, Africa and Australia.

But this latest discovery and some other recent finds indicate that the dinosaur group was well established in Europe and the northern continents - then Laurasia - too.

C. corcovatus was a more primitive member of this group, however, since its body type differed from some of the more advanced forms, like the enormous Carcharodontosaurus.

"This is a very important paper because it provides evidence that feathers were far more widespread among theropod dinosaurs - the predecessors of birds - than we previously thought," says Luis Chiappe, director of The Dinosaur Institute at the Natural History Museum of Los Angeles County, told Discovery News.

"It also shows that feathers were not restricted to just small dinosaurs, even if they didn't have to cover their entire bodies," Chiappe adds. "This fossil offers additional support documenting the dinosaurian ancestry of birds and the claim that birds are living dinosaurs."